NEW YORK A costly months-long battle over the direction of one of America's biggest companies culminates tomorrow with a shareholder vote at Procter & Gamble (P&G) headquarters in Cincinnati.

The fight pits the maker of Gillette razors and Olay soap against activist investor Nelson Peltz, 75, a billionaire hedge fund chief who has pitched himself as the outsider needed to reignite P&G, the largest company by market capitalisation ever to face a proxy battle.

The grizzled veteran of high-profile boardroom brawls accuses the company of operating with excessive cost, being weak on innovation and missing the boat on key shifts in consumer behaviour.

His campaign has been fortified by support from respected proxy advisory services, including Glass Lewis, which said a new voice might help reinvigorate a giant that appears to suffer from a "degree of complacency".

P&G counters that Mr Peltz's campaign is based on an outdated perspective and ignores key hires of outsiders as well as progress since its 2014 decision to divest dozens of underperforming products to target giant brands that resonate best with consumers.